Patent GB-1496734-A (GB)
Title: Sheet feeding and separating
IPC: B65H3/04
Filed: 1975-05-19
Abstract: 1496734 Feeding sheets XEROX CORP 19 May 1975 [5 Sept 1974] 21237/75 Heading B8 Sheet feeding apparatus comprises a sheet separator and retard means forming a nip for sheet advancement therebetween, and means for varying the nip force according to whether a sheet is being fed forwards through the nip or pulled backwards out of the nip, the force being less in the latter case. Pile supports.-A pile of sheets is supported on the base 44, Figs. 2, 6 and 7, of a drawer between a fixed side guide 32 having vertical ribs 34 and an adjustable side guide 33. The drawer is retractable, together with the separator and retard means, along rails 51 to the position of Fig. 2 for loading or for releasing jammed sheets from the nip, and as the drawer is retracted, a front guide 42 is moved upwards so that the front of the pile can be aligned against it. An upper member 70 has upwardly bent side positions 71 to accommodate sheets with upwardly curled edges. Provided that the drawer is in operative feeding position and that a pile P<SP>1</SP> is present, a switch 54, Fig. 5B, mounted in a fixed position, is actuated by a lever 56 to give a signal. If the drawer is retracted, the actuator is remote from the switch, and if no pile is present the lever 56 rises through a slot in the base 44 and does not actuate the switch. Sheet separating.-Sheets are separated from the top of the pile by a friction belt 17 which is mounted on a frame 13 pivotable about a shaft 14, and forms a nip with a retard pad 38, Fig. 6, also mounted on the frame. The belt is driven by a motor M through a shaft 26, a gear 48, Fig. 5B, a gear 47, a clutch 50, the shaft 14, a belt 20 and a shaft 15, Fig. 6. When the drawer is retracted, a cam 36 raises the separator clear of the pile by pivoting about the shaft 14. The pad 38 has a curved surface adjacent the belt 17 and is pivoted about a pin 61 downstream of its centre, so that as a sheet is fed through the nip the pad is moved counterclockwise in Fig. 6 to increase its pressure against the belt, while if a jammed sheet is pulled backwards the pad is moved clockwise to reduce the pressure. Registering sheets.-Each sheet is advanced against a movable stop consisting of tab portions 130, Fig. 7 of a pivoted gate 80, its leading edge being held against the stop by contact with rotating rollers 27, and the sheet is further advanced to form a buckle, Fig. 7. A leveractuated switch 81 or a photo-electric detector senses the leading edge of the sheet before it reaches the stop and initiates a timing control which, after a predetermined delay to produce the desired size of buckle, disengages the clutch 50 to stop the drive of the belt 17. The gate 80 is pivoted clockwise in Fig. 7 by a cam 30, Fig. 2, to release the sheet, which advances into the nip between the rollers 27 and rollers 24, by which it is forwarded while still held between the belt 17 and pad 38. If a sheet is not present at the switch 81 when it should be, the apparatus is stopped. As the sheet is advanced, the flattening of the buckle is assisted by the gate 80 engaging the front part of the buckle and by pivoted members 140 or pivoted strips 141, Fig. 14, of "Mylar" (Registered Trade Mark). In another form, Fig. 12, the stop 80<SP>1</SP> is mounted below the feed path and the buckle is flattened by a flexible member 171 connected between a fixed member and the stop so as to be straightened as the stop moves counterclockwise out of the sheet path. The feed table member 43, Fig. 7, is omitted in the form of Fig. 12 and replaced by the member 171. Sheet forwarding.-During sheet separation, the force of the sepaator against the pile due to its weight is increased by a force caused by the rotation of the shaft 14. When the rollers 27, 24 are advancing the sheet, the latter force is not present since the separator is not being driven, wherefore the trailing of the sheet can be easily pulled clear of the separator. Separating from two piles.-Sheets may be separated from either a lower pile by a top feeder 150, Fig. 14, as discribed above, or from an upper pile by a bottom feeder 160. In the feeder 160, the retard pad 38<SP>11</SP> is above the separator belt 17<SP>11</SP>, and the pressure of the belt against the pile is resisted by a pad 202 on a lever 201 pivoted on a shaft 203 through a one-way clutch 204 which allows movement of the pad towards the pile, but requires the imposition of a force in excess of said pressure to over-ride the clutch and raise the pad for re-loading.  Sheet smoothers.-The sheet is fed over a table member 43, Fig. 7, which has a portion 43<SP>1</SP> roughly conforming to the feed portion of the belt 17. Wrinkles formed due to the separator engaging only a centre part and the rollers 27, 24 engaging the whole width of the sheet are removed by means of a bump 210, Fig. 7, in the member 43, or by mounting the outer rollers 220, 221, Fig. 18A, of the roller assembly 24 so as to be carried in the direction shown. The sheets may be fed to a xerographic machine 230, Fig. 14.